Carbureter of the overflow type

ABSTRACT

A carbureter of the overflow type which is provided with a partition wall and/or a screen in a fuel chamber of the carbureter for controlling the flow of fuel so as to stabilize a fuel layer in the vicinity of a fuel jet of the carbureter.

United States Patent Nishihara 1 1 Oct. 3, 1972 [s41 CARBURETER OF THEOVERFLOW 2,454,974 11/1948 Mennesson ..261/D1G. 50 TYPE 1,025,814 5/1912Lemp ..261/D1G, 50 a]. u n I 4 I n I Kaigan Kanagawa Pref chigasaki3,372,912 3/1968 Benmore ..261/D1G. 50 Japan 3,540,701 11/1970 Brenneke..261/36 A [22] Fil d; N 12, 1970 FOREIGN PATENTS OR APPLICATIONS [21]Appl. No.: 88,698 767,341 5/1934 France ..261/36 A 931,260 10/1947France ..261/36 A [30] Foreign Application Priority Data Primary MilesJune 8, 1970 Japan ..45/56368 A 0rneyMcG1ew & Toren [52] US. Cl...261/36 A, 261/72 R, 261/D1G. 50 [57] ABSTRACT [51] Int. Cl ..F02m37/06 A Carbureter of the overflow t ype which is provided [58] Field ofSearch ..26l/DIG. 50, 36 A, 72 R with a partition wan and/Or a screen ina fuel chamber 56 R f Ct d of the carbureter for controlling the flow offuel so as l 1 e erences I e to stabilize a fuel layer in the vicinityof a fuel jet of UNITED STATES PATENTS the carbureter- 3,275,307 9/1966Robechand ..26l/DIG. 50 2 Claims, 5 Drawing Figures PBTENTEflum 3 m2SHEET 1 0F 2 V YOSIIIO msmui izi BY W: W m0 7mm ATTORNEYS PATENTEDnm m23.695.590

sum 2 or 2 INVENTOR. Yoslflo NISHIHARA WW 761m ATTORNEYS CARBURETER OFTHE OVERFLOW TYPE BACKGROUND OF THE INVENTION This invention relates tocarbureters of the the overflow type, and more particularly it isconcerned with an improvement in or relating to a carbureter fuelchamber.

Carbureters of the overflow type are generally used with motor cycles.The carbureter of this type is adapted to supply fuel to its fuelchamber by gravity when its fuel tank is disposed at a level higher thanthat of the fuel chamber; and when the fuel tank is disposed at a levellower than that of the fuel chamber, fuel is drawn by suction by meansof a pump and the liquid level in the fuel chamber is maintainedconstant at all time by overflowing excess fuel.

The carbureter of this type is simple in construction. However, thedesigning of the carbureter of this type dictates that the orifice of afuel inlet port must not have a large area. Because of this, the fuelnewly introduced into the fuel chamber forms a current flowing at asubstantial flow rate. This fuel current disturbs a fuel layer in thevicinityof a fuel jet, thereby causing fluctuations to occur in thequantity of fuel injected into a mixing passage.

SUMMARY OF THE INVENTION This invention has as its object the provisionof a carbureter of the overflow type which is provided, in its fuelchamber, with buffer means, such as a throttling portion, cylindricalpartition wall, screen, porous member or horizontal plate, either singlyor in combination, for reducing the flow rate of fuel delivered to. thefuel chamber, so as to thereby stabilize a fuel layer in the vicinity ofa fuel jet. The invention offers the advantage of permitting to injectfuel into a mixing passage of the carbureter in a quantity which iscommensurate with engine speed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectionalview of the carbureter of the overflow type comprising one embodiment ofthis invention in which a horizontal plate is mounted in an overflowwall portion in a fuel chamber of the carbureter;

FIG. 2 is a view similar to FIG. 1 but comprising another embodiment ofthe invention in which a screen is mounted;

FIG. 3 is a view similar to FIG. 1 but comprising still anotherembodiment of the invention in which a screen is mounted horizontally ina middle portion of the fuel chamber;

FIG. 4 is a view similar to FIG. 1 but comprising still anotherembodiment of the invention in which a cylindrical partition wall ismounted; and

FIG. 5 is a view similar to FIG. 1 but comprising the other embodimentof the invention in which acylindrical partition wall and a cylindricalscreen are mounted.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION FIG. 1 shows afirst embodiment of the carbureter of the overflow type according tothis invention. The carbureter shown is of the type in which a fuel tank11 is disposed at a level higher than that of a fuel chamber 12 of thecarbureter 10. The fuel in the fuel tank 11 is supplied to the fuelchamber 12 as it flows by gravity when a fuel cock 28 in a fuel supplyline 27 is opened.

The fuel chamber 12 is divided into a fuel well 14 and an overflowchamber 15 by a wall 13. An inlet port 16 communicating with the fuelsupply line 27 is formed in the fuel well 14. A cylindrical member 17enclosing an emulsion tube 18 extends from a lower portion of thecarbureter body into a central portion of the fuel well 14. A horizontalportion 20 extends inwardly from an upper end of the wall 13 toward thecylindrical member 17 and spaced therefrom by a small gap or a throttleportion 19. A main jet 21 is formed at a lower end of the emulsion tube18, and a main nozzle 23 is provided at an upper end thereof to openinto a Venturi portion 22 of the carbureter 10.

The fuel delivered by passing through the fuel inlet port 16 is passedthrough the main jet 21 and injected into a mixing passage 24 throughthe main nozzle 23. The quantity of fuel injected into the mixingpassage varies depending on engine speed. The quantity of injected fuelis reduced when the engine speed is low or the engine is idling becausea negative pressure in the mixing passage 24 of the carbureter 10 isreduced. When this is the case, the fuel introduced into the fuelchamber 12 fills the fuel well 14 and excess fuel overflows through thegap 19 into the chamber 15. The excess fuel passed into the chamber 15is returned through an outlet port 26 and a return passage 29 to thefuel tank 11 by means of a pump 30 operated in conjunction with thedriving of the engine.

The carbureter of the overflow type according to one aspect of thisinvention is constructed as aforementioned. The invention permits tostore a large quantity of fuel in the fuel well 14 at all times. If thecock 28 is operated in conjunction with the starting of the engine, thena rate of reduction of the liquid level in the fuel well 14 is not sogreat by virtue of the automatic operation of the cock 28 even if thefuel delivered from the fuel tank 11 to the fuel well 14 through thefuel supply line 27 is smaller in quantity than the fuel passed from thefuel well 14 through the main jet 21 into the main nozzle 23 to beinjected into the mixing passage 24. With this arrangement, a shortageof fuel does not occur when the engine is started. When the carbureteras a whole is swayed to and fro by vibrations of high magnitude whilethe consumption of fuel is small in quantity and the liquid level in thefuel well 14 is almost flush with the liquid level in the overflowchamber 15, the gap 19 serves as a throttling portion and prevents thesplashing of the fuel in the fuel well 14 into the overflow chamber 15.When the fuel delivered through the fuel supply line 27 to the fuel well14 is greater in quantity than the fuel consumed, such as when the engine speed is low or the engine is idling, excess fuel is spilledthrough the outlet port 26 of the overflow chamber 15 and returnedthrough the passage 29 to the fuel tank 11, thereby keeping the liquidlevel in the fuel well 14 constant at all times.

FIG. 2 shows a second embodiment of this invention. In this embodiment,the carbureter comprises buffer means, such as a screen, porous plate orthe like, which is provided horizontally at an upper end of the fuelwell 14 or near the over flow liquid level.

The wall 13 is formed at its upper end with a plurality of smallprojections 31 each of which is formed with an internally threadedportion for receiving therein a screw 33 after a screen 32 is placed onthe projections 31 so as to firmly secure the'screen thereto.

In the third embodiment shown in FIG. 3, a screen 34 is providedhorizontally in the fuel well 14 and disposed at a level higher thanthat of the main jet 21 but lower than that of the fuel inlet port 16.The screen 34 is held in place by screws 35.

Like the first embodiment, the second and third embodiments permitexcess fuel to overflow to be returned to the fuel tank 11. Thus, theliquid level in the fuel well 14 is kept constant at all times and thesplashing of fuel is minimized when the carburetor sways due tovibrations because the screen preforms a throttling action.

The third embodiment shown in FIG. 3 isparticularly effective tomarkedly reduce disturbances in the flow of fuel introduced into thefuel well 14 through the inlet port 16 at a substantial rate by the flowregulating action of the screen or porous plate member which is disposedhorizontally in a middle portion of the fuel well 14. For this reason, alower layer of fuel in the fuel well 14 is stabilized and no turbulentcurrent is formed in the vicinity of the fuel jet (main jet) 21. This isconducive to the prevention of fluctuations in the pressure at the fuelinlet port of the fuel jet 21 which might otherwise be caused by aturbulent flow of fuel and the elimination of fluctuations in thequantity of fuel injected into the mixing passage.

FIG. 4 shows a fourth embodiment which comprises a cylindrical partitionwall 36 mounted vertically in the fuel well 14. The cylindricalpartition wall 36 is slightly smaller in height than the wall 13 anddivides the well 14 into a chamber 40 and an annular space 41. The fueldelivered through the inlet port 16 fills the annular space 41 and thenoverflows the wall 36 into the chamber 40. Then, the fuel is passedthrough the fuel jet 21 and main nozzle 23 to be injected into themixing passage 24. When the quantity of injected fuel is reduced due toengine speed, the fuel in the fuel well 14 overflows into the chamberand is returned to the tank 11.

The fifth embodiment shown in FIG. 5 comprises the cylindrical partitionwall 36 and a screen 37 mounted in the fuel well 14. The annular space41 defined by the cylindrical partition wall 36 is closed at its upperend by an annular plate 38 formed at an upper edge of the par titionwall 36. The partition wall 36 is formed near its upper end with aplurality of small openings 39 through which the annular space 41maintains communication with the chamber 40. In this embodiment, thefuel delivered through the inlet port 16 is stored in the annular space41 and passed through the small openings 39 into the chamber 40 fromwhich it is passed through the fuel jet 21 and injected into the mixingpassage 24 through the main nozzle 23. Thus, the fuel introduced intothe fuel well 14 has its flow rate adjusted by the partition wall 36 andscreen 37, so that a fuel layer in the vicinity of the fuel jet can bestabilized.

Each of the fourth and fifth embodiments controls by means of thepartition wall 36, the flow rate of fuel delivered into the fuel well 14through the inlet port 16 so as to thereb stabilize a fuel 1 er near thef el t 21. The provisi n of the screen 37 i n the chambei 40 i naddition to the wall 36 makes it possible to minimize fluctuations inthe quantity of fuel injected into the mixing passage, even when thefuel is delivered into the fuel well at a considerable rate, by moreefiectively stabilizing a fuel layer in the fuel well in the vicinity ofthe fuel jet than would be the case if there were no screen.

The various embodiments of the present invention have been described asbeing incorporated in carbureters of the type in which the fuel tank 11is disposed at a level higher than that of the fuel chamber 12. It is tobe understood that this invention can be incorporated in carbureters ofthe type in which the fuel tank 11 is disposed at a level lower thanthat of the fuel chamber 12 so that the fuel supplied from the fuel tankis delivered to the fuel chamber of the carbureter by means of a fueldelivery pump and excess fuel overflows and spills back to the fuel tankby gravity.

What I claim is:

1. An overflow type carburetor comprising a carburetor body forming ahorizontal mixing passage including a Venturi portion, walls meanssecured to said carburetor body and forming a fuel chamber located belowsaid mixing passage, a main nozzle support tube positioned within saidfuel chamber, said main nozzle support tube having a main nozzle at itsupper end in communication with said Venturi portion of said mixingpassage and having a main jet at its lower end within said fuel chamber,an upright wall located within said fuel chamber dividing it into a fuelwell and an overflow chamber, an upright cylindrical partition wallpositioned within said fuel well inwardly from said upright wall anddividing said fuel well into an inner chamber containing said mainnozzle support tube with said main jet thereof located below the upperend of said cylindrical partition wall and an annular space encirclingsaid inner chamber, the upper end of said cylindrical partition walllocated below the upper end of said cylindrical partition wall locatedbelow the upper end of said upright wall, said wall means including aninlet port communicating with said annular space for supplying fuel froma supply source into said fuel well and an outlet port in communicationwith the base of said overflow chamber for returning excess fuel to thesupply source so that said cylindrical partition wall affords astabilized fuel layer in said inner chamber in the vicinity of said mainjet for preventing fluctuations in the quantity of fuel injected intosaid mixing passage.

2. An overflow type carburetor, as set forth in claim 1, wherein ahorizontally arranged annular plate is secured to the upper end of andforms a closure for the upper end of said annular space, a plurality ofsmall openings formed in the upper end of said upright cylindricalpartition wall for affording flow from said annular space into saidinner chamber, and a second upright partition wall formed of a perviousmaterial positioned within said inner chamber inwardly of the other saidpartition wall and said second partition wall extending for the heightof said inner chamber and laterally encircling said main nozzle supporttube.

1. An overflow type carburetor comprising a carburetor body forming a horizontal mixing passage including a Venturi portion, walls means secured to said carburetor body and forming a fuel chamber located below said mixing passage, a main nozzle support tube positiOned within said fuel chamber, said main nozzle support tube having a main nozzle at its upper end in communication with said Venturi portion of said mixing passage and having a main jet at its lower end within said fuel chamber, an upright wall located within said fuel chamber dividing it into a fuel well and an overflow chamber, an upright cylindrical partition wall positioned within said fuel well inwardly from said upright wall and dividing said fuel well into an inner chamber containing said main nozzle support tube with said main jet thereof located below the upper end of said cylindrical partition wall and an annular space encircling said inner chamber, the upper end of said cylindrical partition wall located below the upper end of said cylindrical partition wall located below the upper end of said upright wall, said wall means including an inlet port communicating with said annular space for supplying fuel from a supply source into said fuel well and an outlet port in communication with the base of said overflow chamber for returning excess fuel to the supply source so that said cylindrical partition wall affords a stabilized fuel layer in said inner chamber in the vicinity of said main jet for preventing fluctuations in the quantity of fuel injected into said mixing passage.
 2. An overflow type carburetor, as set forth in claim 1, wherein a horizontally arranged annular plate is secured to the upper end of and forms a closure for the upper end of said annular space, a plurality of small openings formed in the upper end of said upright cylindrical partition wall for affording flow from said annular space into said inner chamber, and a second upright partition wall formed of a pervious material positioned within said inner chamber inwardly of the other said partition wall and said second partition wall extending for the height of said inner chamber and laterally encircling said main nozzle support tube. 